lib/Transforms/Instrumentation/ThreadSanitizer.cpp

   1 //===-- ThreadSanitizer.cpp - race detector -------------------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file is a part of ThreadSanitizer, a race detector.
  11 //
  12 // The tool is under development, for the details about previous versions see
  13 // http://code.google.com/p/data-race-test
  14 //
  15 // The instrumentation phase is quite simple:
  16 //   - Insert calls to run-time library before every memory access.
  17 //      - Optimizations may apply to avoid instrumenting some of the accesses.
  18 //   - Insert calls at function entry/exit.
  19 // The rest is handled by the run-time library.
  20 //===----------------------------------------------------------------------===//
  21
  22 #include "llvm/Transforms/Instrumentation.h"
  23 #include "llvm/ADT/SmallSet.h"
  24 #include "llvm/ADT/SmallString.h"
  25 #include "llvm/ADT/SmallVector.h"
  26 #include "llvm/ADT/Statistic.h"
  27 #include "llvm/ADT/StringExtras.h"
  28 #include "llvm/Analysis/CaptureTracking.h"
  29 #include "llvm/Analysis/ValueTracking.h"
  30 #include "llvm/IR/DataLayout.h"
  31 #include "llvm/IR/Function.h"
  32 #include "llvm/IR/IRBuilder.h"
  33 #include "llvm/IR/IntrinsicInst.h"
  34 #include "llvm/IR/Intrinsics.h"
  35 #include "llvm/IR/LLVMContext.h"
  36 #include "llvm/IR/Metadata.h"
  37 #include "llvm/IR/Module.h"
  38 #include "llvm/IR/Type.h"
  39 #include "llvm/Support/CommandLine.h"
  40 #include "llvm/Support/Debug.h"
  41 #include "llvm/Support/MathExtras.h"
  42 #include "llvm/Support/raw_ostream.h"
  43 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
  44 #include "llvm/Transforms/Utils/ModuleUtils.h"
  45
  46 using namespace llvm;
  47
  48 #define DEBUG_TYPE "tsan"
  49
  50 static cl::opt<bool>  ClInstrumentMemoryAccesses(
  51     "tsan-instrument-memory-accesses", cl::init(true),
  52     cl::desc("Instrument memory accesses"), cl::Hidden);
  53 static cl::opt<bool>  ClInstrumentFuncEntryExit(
  54     "tsan-instrument-func-entry-exit", cl::init(true),
  55     cl::desc("Instrument function entry and exit"), cl::Hidden);
  56 static cl::opt<bool>  ClInstrumentAtomics(
  57     "tsan-instrument-atomics", cl::init(true),
  58     cl::desc("Instrument atomics"), cl::Hidden);
  59 static cl::opt<bool>  ClInstrumentMemIntrinsics(
  60     "tsan-instrument-memintrinsics", cl::init(true),
  61     cl::desc("Instrument memintrinsics (memset/memcpy/memmove)"), cl::Hidden);
  62
  63 STATISTIC(NumInstrumentedReads, "Number of instrumented reads");
  64 STATISTIC(NumInstrumentedWrites, "Number of instrumented writes");
  65 STATISTIC(NumOmittedReadsBeforeWrite,
  66           "Number of reads ignored due to following writes");
  67 STATISTIC(NumAccessesWithBadSize, "Number of accesses with bad size");
  68 STATISTIC(NumInstrumentedVtableWrites, "Number of vtable ptr writes");
  69 STATISTIC(NumInstrumentedVtableReads, "Number of vtable ptr reads");
  70 STATISTIC(NumOmittedReadsFromConstantGlobals,
  71           "Number of reads from constant globals");
  72 STATISTIC(NumOmittedReadsFromVtable, "Number of vtable reads");
  73 STATISTIC(NumOmittedNonCaptured, "Number of accesses ignored due to capturing");
  74
  75 static const char *const kTsanModuleCtorName = "tsan.module_ctor";
  76 static const char *const kTsanInitName = "__tsan_init";
  77
  78 namespace {
  79
  80 /// ThreadSanitizer: instrument the code in module to find races.
  81 struct ThreadSanitizer : public FunctionPass {
  82   ThreadSanitizer() : FunctionPass(ID) {}
  83   const char *getPassName() const override;
  84   bool runOnFunction(Function &F) override;
  85   bool doInitialization(Module &M) override;
  86   static char ID;  // Pass identification, replacement for typeid.
  87
  88  private:
  89   void initializeCallbacks(Module &M);
  90   bool instrumentLoadOrStore(Instruction *I, const DataLayout &DL);
  91   bool instrumentAtomic(Instruction *I, const DataLayout &DL);
  92   bool instrumentMemIntrinsic(Instruction *I);
  93   void chooseInstructionsToInstrument(SmallVectorImpl<Instruction *> &Local,
  94                                       SmallVectorImpl<Instruction *> &All,
  95                                       const DataLayout &DL);
  96   bool addrPointsToConstantData(Value *Addr);
  97   int getMemoryAccessFuncIndex(Value *Addr, const DataLayout &DL);
  98
  99   Type *IntptrTy;
 100   IntegerType *OrdTy;
 101   // Callbacks to run-time library are computed in doInitialization.
 102   Function *TsanFuncEntry;
 103   Function *TsanFuncExit;
 104   // Accesses sizes are powers of two: 1, 2, 4, 8, 16.
 105   static const size_t kNumberOfAccessSizes = 5;
 106   Function *TsanRead[kNumberOfAccessSizes];
 107   Function *TsanWrite[kNumberOfAccessSizes];
 108   Function *TsanUnalignedRead[kNumberOfAccessSizes];
 109   Function *TsanUnalignedWrite[kNumberOfAccessSizes];
 110   Function *TsanAtomicLoad[kNumberOfAccessSizes];
 111   Function *TsanAtomicStore[kNumberOfAccessSizes];
 112   Function *TsanAtomicRMW[AtomicRMWInst::LAST_BINOP + 1][kNumberOfAccessSizes];
 113   Function *TsanAtomicCAS[kNumberOfAccessSizes];
 114   Function *TsanAtomicThreadFence;
 115   Function *TsanAtomicSignalFence;
 116   Function *TsanVptrUpdate;
 117   Function *TsanVptrLoad;
 118   Function *MemmoveFn, *MemcpyFn, *MemsetFn;
 119   Function *TsanCtorFunction;
 120 };
 121 }  // namespace
 122
 123 char ThreadSanitizer::ID = 0;
 124 INITIALIZE_PASS(ThreadSanitizer, "tsan",
 125     "ThreadSanitizer: detects data races.",
 126     false, false)
 127
 128 const char *ThreadSanitizer::getPassName() const {
 129   return "ThreadSanitizer";
 130 }
 131
 132 FunctionPass *llvm::createThreadSanitizerPass() {
 133   return new ThreadSanitizer();
 134 }
 135
 136 void ThreadSanitizer::initializeCallbacks(Module &M) {
 137   IRBuilder<> IRB(M.getContext());
 138   // Initialize the callbacks.
 139   TsanFuncEntry = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 140       "__tsan_func_entry", IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
 141   TsanFuncExit = checkSanitizerInterfaceFunction(
 142       M.getOrInsertFunction("__tsan_func_exit", IRB.getVoidTy(), nullptr));
 143   OrdTy = IRB.getInt32Ty();
 144   for (size_t i = 0; i < kNumberOfAccessSizes; ++i) {
 145     const size_t ByteSize = 1 << i;
 146     const size_t BitSize = ByteSize * 8;
 147     SmallString<32> ReadName("__tsan_read" + itostr(ByteSize));
 148     TsanRead[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 149         ReadName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
 150
 151     SmallString<32> WriteName("__tsan_write" + itostr(ByteSize));
 152     TsanWrite[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 153         WriteName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
 154
 155     SmallString<64> UnalignedReadName("__tsan_unaligned_read" +
 156         itostr(ByteSize));
 157     TsanUnalignedRead[i] =
 158         checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 159             UnalignedReadName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
 160
 161     SmallString<64> UnalignedWriteName("__tsan_unaligned_write" +
 162         itostr(ByteSize));
 163     TsanUnalignedWrite[i] =
 164         checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 165             UnalignedWriteName, IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
 166
 167     Type *Ty = Type::getIntNTy(M.getContext(), BitSize);
 168     Type *PtrTy = Ty->getPointerTo();
 169     SmallString<32> AtomicLoadName("__tsan_atomic" + itostr(BitSize) +
 170                                    "_load");
 171     TsanAtomicLoad[i] = checkSanitizerInterfaceFunction(
 172         M.getOrInsertFunction(AtomicLoadName, Ty, PtrTy, OrdTy, nullptr));
 173
 174     SmallString<32> AtomicStoreName("__tsan_atomic" + itostr(BitSize) +
 175                                     "_store");
 176     TsanAtomicStore[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 177         AtomicStoreName, IRB.getVoidTy(), PtrTy, Ty, OrdTy, nullptr));
 178
 179     for (int op = AtomicRMWInst::FIRST_BINOP;
 180         op <= AtomicRMWInst::LAST_BINOP; ++op) {
 181       TsanAtomicRMW[op][i] = nullptr;
 182       const char *NamePart = nullptr;
 183       if (op == AtomicRMWInst::Xchg)
 184         NamePart = "_exchange";
 185       else if (op == AtomicRMWInst::Add)
 186         NamePart = "_fetch_add";
 187       else if (op == AtomicRMWInst::Sub)
 188         NamePart = "_fetch_sub";
 189       else if (op == AtomicRMWInst::And)
 190         NamePart = "_fetch_and";
 191       else if (op == AtomicRMWInst::Or)
 192         NamePart = "_fetch_or";
 193       else if (op == AtomicRMWInst::Xor)
 194         NamePart = "_fetch_xor";
 195       else if (op == AtomicRMWInst::Nand)
 196         NamePart = "_fetch_nand";
 197       else
 198         continue;
 199       SmallString<32> RMWName("__tsan_atomic" + itostr(BitSize) + NamePart);
 200       TsanAtomicRMW[op][i] = checkSanitizerInterfaceFunction(
 201           M.getOrInsertFunction(RMWName, Ty, PtrTy, Ty, OrdTy, nullptr));
 202     }
 203
 204     SmallString<32> AtomicCASName("__tsan_atomic" + itostr(BitSize) +
 205                                   "_compare_exchange_val");
 206     TsanAtomicCAS[i] = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 207         AtomicCASName, Ty, PtrTy, Ty, Ty, OrdTy, OrdTy, nullptr));
 208   }
 209   TsanVptrUpdate = checkSanitizerInterfaceFunction(
 210       M.getOrInsertFunction("__tsan_vptr_update", IRB.getVoidTy(),
 211                             IRB.getInt8PtrTy(), IRB.getInt8PtrTy(), nullptr));
 212   TsanVptrLoad = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 213       "__tsan_vptr_read", IRB.getVoidTy(), IRB.getInt8PtrTy(), nullptr));
 214   TsanAtomicThreadFence = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 215       "__tsan_atomic_thread_fence", IRB.getVoidTy(), OrdTy, nullptr));
 216   TsanAtomicSignalFence = checkSanitizerInterfaceFunction(M.getOrInsertFunction(
 217       "__tsan_atomic_signal_fence", IRB.getVoidTy(), OrdTy, nullptr));
 218
 219   MemmoveFn = checkSanitizerInterfaceFunction(
 220       M.getOrInsertFunction("memmove", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
 221                             IRB.getInt8PtrTy(), IntptrTy, nullptr));
 222   MemcpyFn = checkSanitizerInterfaceFunction(
 223       M.getOrInsertFunction("memcpy", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
 224                             IRB.getInt8PtrTy(), IntptrTy, nullptr));
 225   MemsetFn = checkSanitizerInterfaceFunction(
 226       M.getOrInsertFunction("memset", IRB.getInt8PtrTy(), IRB.getInt8PtrTy(),
 227                             IRB.getInt32Ty(), IntptrTy, nullptr));
 228 }
 229
 230 bool ThreadSanitizer::doInitialization(Module &M) {
 231   const DataLayout &DL = M.getDataLayout();
 232   IntptrTy = DL.getIntPtrType(M.getContext());
 233   std::tie(TsanCtorFunction, std::ignore) = createSanitizerCtorAndInitFunctions(
 234       M, kTsanModuleCtorName, kTsanInitName, /*InitArgTypes=*/{},
 235       /*InitArgs=*/{});
 236
 237   appendToGlobalCtors(M, TsanCtorFunction, 0);
 238
 239   return true;
 240 }
 241
 242 static bool isVtableAccess(Instruction *I) {
 243   if (MDNode *Tag = I->getMetadata(LLVMContext::MD_tbaa))
 244     return Tag->isTBAAVtableAccess();
 245   return false;
 246 }
 247
 248 bool ThreadSanitizer::addrPointsToConstantData(Value *Addr) {
 249   // If this is a GEP, just analyze its pointer operand.
 250   if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Addr))
 251     Addr = GEP->getPointerOperand();
 252
 253   if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
 254     if (GV->isConstant()) {
 255       // Reads from constant globals can not race with any writes.
 256       NumOmittedReadsFromConstantGlobals++;
 257       return true;
 258     }
 259   } else if (LoadInst *L = dyn_cast<LoadInst>(Addr)) {
 260     if (isVtableAccess(L)) {
 261       // Reads from a vtable pointer can not race with any writes.
 262       NumOmittedReadsFromVtable++;
 263       return true;
 264     }
 265   }
 266   return false;
 267 }
 268
 269 // Instrumenting some of the accesses may be proven redundant.
 270 // Currently handled:
 271 //  - read-before-write (within same BB, no calls between)
 272 //  - not captured variables
 273 //
 274 // We do not handle some of the patterns that should not survive
 275 // after the classic compiler optimizations.
 276 // E.g. two reads from the same temp should be eliminated by CSE,
 277 // two writes should be eliminated by DSE, etc.
 278 //
 279 // 'Local' is a vector of insns within the same BB (no calls between).
 280 // 'All' is a vector of insns that will be instrumented.
 281 void ThreadSanitizer::chooseInstructionsToInstrument(
 282     SmallVectorImpl<Instruction *> &Local, SmallVectorImpl<Instruction *> &All,
 283     const DataLayout &DL) {
 284   SmallSet<Value*, 8> WriteTargets;
 285   // Iterate from the end.
 286   for (SmallVectorImpl<Instruction*>::reverse_iterator It = Local.rbegin(),
 287        E = Local.rend(); It != E; ++It) {
 288     Instruction *I = *It;
 289     if (StoreInst *Store = dyn_cast<StoreInst>(I)) {
 290       WriteTargets.insert(Store->getPointerOperand());
 291     } else {
 292       LoadInst *Load = cast<LoadInst>(I);
 293       Value *Addr = Load->getPointerOperand();
 294       if (WriteTargets.count(Addr)) {
 295         // We will write to this temp, so no reason to analyze the read.
 296         NumOmittedReadsBeforeWrite++;
 297         continue;
 298       }
 299       if (addrPointsToConstantData(Addr)) {
 300         // Addr points to some constant data -- it can not race with any writes.
 301         continue;
 302       }
 303     }
 304     Value *Addr = isa<StoreInst>(*I)
 305         ? cast<StoreInst>(I)->getPointerOperand()
 306         : cast<LoadInst>(I)->getPointerOperand();
 307     if (isa<AllocaInst>(GetUnderlyingObject(Addr, DL)) &&
 308         !PointerMayBeCaptured(Addr, true, true)) {
 309       // The variable is addressable but not captured, so it cannot be
 310       // referenced from a different thread and participate in a data race
 311       // (see llvm/Analysis/CaptureTracking.h for details).
 312       NumOmittedNonCaptured++;
 313       continue;
 314     }
 315     All.push_back(I);
 316   }
 317   Local.clear();
 318 }
 319
 320 static bool isAtomic(Instruction *I) {
 321   if (LoadInst *LI = dyn_cast<LoadInst>(I))
 322     return LI->isAtomic() && LI->getSynchScope() == CrossThread;
 323   if (StoreInst *SI = dyn_cast<StoreInst>(I))
 324     return SI->isAtomic() && SI->getSynchScope() == CrossThread;
 325   if (isa<AtomicRMWInst>(I))
 326     return true;
 327   if (isa<AtomicCmpXchgInst>(I))
 328     return true;
 329   if (isa<FenceInst>(I))
 330     return true;
 331   return false;
 332 }
 333
 334 bool ThreadSanitizer::runOnFunction(Function &F) {
 335   // This is required to prevent instrumenting call to __tsan_init from within
 336   // the module constructor.
 337   if (&F == TsanCtorFunction)
 338     return false;
 339   initializeCallbacks(*F.getParent());
 340   SmallVector<Instruction*, 8> RetVec;
 341   SmallVector<Instruction*, 8> AllLoadsAndStores;
 342   SmallVector<Instruction*, 8> LocalLoadsAndStores;
 343   SmallVector<Instruction*, 8> AtomicAccesses;
 344   SmallVector<Instruction*, 8> MemIntrinCalls;
 345   bool Res = false;
 346   bool HasCalls = false;
 347   bool SanitizeFunction = F.hasFnAttribute(Attribute::SanitizeThread);
 348   const DataLayout &DL = F.getParent()->getDataLayout();
 349
 350   // Traverse all instructions, collect loads/stores/returns, check for calls.
 351   for (auto &BB : F) {
 352     for (auto &Inst : BB) {
 353       if (isAtomic(&Inst))
 354         AtomicAccesses.push_back(&Inst);
 355       else if (isa<LoadInst>(Inst) || isa<StoreInst>(Inst))
 356         LocalLoadsAndStores.push_back(&Inst);
 357       else if (isa<ReturnInst>(Inst))
 358         RetVec.push_back(&Inst);
 359       else if (isa<CallInst>(Inst) || isa<InvokeInst>(Inst)) {
 360         if (isa<MemIntrinsic>(Inst))
 361           MemIntrinCalls.push_back(&Inst);
 362         HasCalls = true;
 363         chooseInstructionsToInstrument(LocalLoadsAndStores, AllLoadsAndStores,
 364                                        DL);
 365       }
 366     }
 367     chooseInstructionsToInstrument(LocalLoadsAndStores, AllLoadsAndStores, DL);
 368   }
 369
 370   // We have collected all loads and stores.
 371   // FIXME: many of these accesses do not need to be checked for races
 372   // (e.g. variables that do not escape, etc).
 373
 374   // Instrument memory accesses only if we want to report bugs in the function.
 375   if (ClInstrumentMemoryAccesses && SanitizeFunction)
 376     for (auto Inst : AllLoadsAndStores) {
 377       Res |= instrumentLoadOrStore(Inst, DL);
 378     }
 379
 380   // Instrument atomic memory accesses in any case (they can be used to
 381   // implement synchronization).
 382   if (ClInstrumentAtomics)
 383     for (auto Inst : AtomicAccesses) {
 384       Res |= instrumentAtomic(Inst, DL);
 385     }
 386
 387   if (ClInstrumentMemIntrinsics && SanitizeFunction)
 388     for (auto Inst : MemIntrinCalls) {
 389       Res |= instrumentMemIntrinsic(Inst);
 390     }
 391
 392   // Instrument function entry/exit points if there were instrumented accesses.
 393   if ((Res || HasCalls) && ClInstrumentFuncEntryExit) {
 394     IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
 395     Value *ReturnAddress = IRB.CreateCall(
 396         Intrinsic::getDeclaration(F.getParent(), Intrinsic::returnaddress),
 397         IRB.getInt32(0));
 398     IRB.CreateCall(TsanFuncEntry, ReturnAddress);
 399     for (auto RetInst : RetVec) {
 400       IRBuilder<> IRBRet(RetInst);
 401       IRBRet.CreateCall(TsanFuncExit, {});
 402     }
 403     Res = true;
 404   }
 405   return Res;
 406 }
 407
 408 bool ThreadSanitizer::instrumentLoadOrStore(Instruction *I,
 409                                             const DataLayout &DL) {
 410   IRBuilder<> IRB(I);
 411   bool IsWrite = isa<StoreInst>(*I);
 412   Value *Addr = IsWrite
 413       ? cast<StoreInst>(I)->getPointerOperand()
 414       : cast<LoadInst>(I)->getPointerOperand();
 415   int Idx = getMemoryAccessFuncIndex(Addr, DL);
 416   if (Idx < 0)
 417     return false;
 418   if (IsWrite && isVtableAccess(I)) {
 419     DEBUG(dbgs() << "  VPTR : " << *I << "\n");
 420     Value *StoredValue = cast<StoreInst>(I)->getValueOperand();
 421     // StoredValue may be a vector type if we are storing several vptrs at once.
 422     // In this case, just take the first element of the vector since this is
 423     // enough to find vptr races.
 424     if (isa<VectorType>(StoredValue->getType()))
 425       StoredValue = IRB.CreateExtractElement(
 426           StoredValue, ConstantInt::get(IRB.getInt32Ty(), 0));
 427     if (StoredValue->getType()->isIntegerTy())
 428       StoredValue = IRB.CreateIntToPtr(StoredValue, IRB.getInt8PtrTy());
 429     // Call TsanVptrUpdate.
 430     IRB.CreateCall(TsanVptrUpdate,
 431                    {IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()),
 432                     IRB.CreatePointerCast(StoredValue, IRB.getInt8PtrTy())});
 433     NumInstrumentedVtableWrites++;
 434     return true;
 435   }
 436   if (!IsWrite && isVtableAccess(I)) {
 437     IRB.CreateCall(TsanVptrLoad,
 438                    IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
 439     NumInstrumentedVtableReads++;
 440     return true;
 441   }
 442   const unsigned Alignment = IsWrite
 443       ? cast<StoreInst>(I)->getAlignment()
 444       : cast<LoadInst>(I)->getAlignment();
 445   Type *OrigTy = cast<PointerType>(Addr->getType())->getElementType();
 446   const uint32_t TypeSize = DL.getTypeStoreSizeInBits(OrigTy);
 447   Value *OnAccessFunc = nullptr;
 448   if (Alignment == 0 || Alignment >= 8 || (Alignment % (TypeSize / 8)) == 0)
 449     OnAccessFunc = IsWrite ? TsanWrite[Idx] : TsanRead[Idx];
 450   else
 451     OnAccessFunc = IsWrite ? TsanUnalignedWrite[Idx] : TsanUnalignedRead[Idx];
 452   IRB.CreateCall(OnAccessFunc, IRB.CreatePointerCast(Addr, IRB.getInt8PtrTy()));
 453   if (IsWrite) NumInstrumentedWrites++;
 454   else         NumInstrumentedReads++;
 455   return true;
 456 }
 457
 458 static ConstantInt *createOrdering(IRBuilder<> *IRB, AtomicOrdering ord) {
 459   uint32_t v = 0;
 460   switch (ord) {
 461     case NotAtomic: llvm_unreachable("unexpected atomic ordering!");
 462     case Unordered:              // Fall-through.
 463     case Monotonic:              v = 0; break;
 464     // case Consume:                v = 1; break;  // Not specified yet.
 465     case Acquire:                v = 2; break;
 466     case Release:                v = 3; break;
 467     case AcquireRelease:         v = 4; break;
 468     case SequentiallyConsistent: v = 5; break;
 469   }
 470   return IRB->getInt32(v);
 471 }
 472
 473 // If a memset intrinsic gets inlined by the code gen, we will miss races on it.
 474 // So, we either need to ensure the intrinsic is not inlined, or instrument it.
 475 // We do not instrument memset/memmove/memcpy intrinsics (too complicated),
 476 // instead we simply replace them with regular function calls, which are then
 477 // intercepted by the run-time.
 478 // Since tsan is running after everyone else, the calls should not be
 479 // replaced back with intrinsics. If that becomes wrong at some point,
 480 // we will need to call e.g. __tsan_memset to avoid the intrinsics.
 481 bool ThreadSanitizer::instrumentMemIntrinsic(Instruction *I) {
 482   IRBuilder<> IRB(I);
 483   if (MemSetInst *M = dyn_cast<MemSetInst>(I)) {
 484     IRB.CreateCall(
 485         MemsetFn,
 486         {IRB.CreatePointerCast(M->getArgOperand(0), IRB.getInt8PtrTy()),
 487          IRB.CreateIntCast(M->getArgOperand(1), IRB.getInt32Ty(), false),
 488          IRB.CreateIntCast(M->getArgOperand(2), IntptrTy, false)});
 489     I->eraseFromParent();
 490   } else if (MemTransferInst *M = dyn_cast<MemTransferInst>(I)) {
 491     IRB.CreateCall(
 492         isa<MemCpyInst>(M) ? MemcpyFn : MemmoveFn,
 493         {IRB.CreatePointerCast(M->getArgOperand(0), IRB.getInt8PtrTy()),
 494          IRB.CreatePointerCast(M->getArgOperand(1), IRB.getInt8PtrTy()),
 495          IRB.CreateIntCast(M->getArgOperand(2), IntptrTy, false)});
 496     I->eraseFromParent();
 497   }
 498   return false;
 499 }
 500
 501 // Both llvm and ThreadSanitizer atomic operations are based on C++11/C1x
 502 // standards.  For background see C++11 standard.  A slightly older, publicly
 503 // available draft of the standard (not entirely up-to-date, but close enough
 504 // for casual browsing) is available here:
 505 // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3242.pdf
 506 // The following page contains more background information:
 507 // http://www.hpl.hp.com/personal/Hans_Boehm/c++mm/
 508
 509 bool ThreadSanitizer::instrumentAtomic(Instruction *I, const DataLayout &DL) {
 510   IRBuilder<> IRB(I);
 511   if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
 512     Value *Addr = LI->getPointerOperand();
 513     int Idx = getMemoryAccessFuncIndex(Addr, DL);
 514     if (Idx < 0)
 515       return false;
 516     const size_t ByteSize = 1 << Idx;
 517     const size_t BitSize = ByteSize * 8;
 518     Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
 519     Type *PtrTy = Ty->getPointerTo();
 520     Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
 521                      createOrdering(&IRB, LI->getOrdering())};
 522     CallInst *C = CallInst::Create(TsanAtomicLoad[Idx], Args);
 523     ReplaceInstWithInst(I, C);
 524
 525   } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
 526     Value *Addr = SI->getPointerOperand();
 527     int Idx = getMemoryAccessFuncIndex(Addr, DL);
 528     if (Idx < 0)
 529       return false;
 530     const size_t ByteSize = 1 << Idx;
 531     const size_t BitSize = ByteSize * 8;
 532     Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
 533     Type *PtrTy = Ty->getPointerTo();
 534     Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
 535                      IRB.CreateIntCast(SI->getValueOperand(), Ty, false),
 536                      createOrdering(&IRB, SI->getOrdering())};
 537     CallInst *C = CallInst::Create(TsanAtomicStore[Idx], Args);
 538     ReplaceInstWithInst(I, C);
 539   } else if (AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(I)) {
 540     Value *Addr = RMWI->getPointerOperand();
 541     int Idx = getMemoryAccessFuncIndex(Addr, DL);
 542     if (Idx < 0)
 543       return false;
 544     Function *F = TsanAtomicRMW[RMWI->getOperation()][Idx];
 545     if (!F)
 546       return false;
 547     const size_t ByteSize = 1 << Idx;
 548     const size_t BitSize = ByteSize * 8;
 549     Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
 550     Type *PtrTy = Ty->getPointerTo();
 551     Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
 552                      IRB.CreateIntCast(RMWI->getValOperand(), Ty, false),
 553                      createOrdering(&IRB, RMWI->getOrdering())};
 554     CallInst *C = CallInst::Create(F, Args);
 555     ReplaceInstWithInst(I, C);
 556   } else if (AtomicCmpXchgInst *CASI = dyn_cast<AtomicCmpXchgInst>(I)) {
 557     Value *Addr = CASI->getPointerOperand();
 558     int Idx = getMemoryAccessFuncIndex(Addr, DL);
 559     if (Idx < 0)
 560       return false;
 561     const size_t ByteSize = 1 << Idx;
 562     const size_t BitSize = ByteSize * 8;
 563     Type *Ty = Type::getIntNTy(IRB.getContext(), BitSize);
 564     Type *PtrTy = Ty->getPointerTo();
 565     Value *Args[] = {IRB.CreatePointerCast(Addr, PtrTy),
 566                      IRB.CreateIntCast(CASI->getCompareOperand(), Ty, false),
 567                      IRB.CreateIntCast(CASI->getNewValOperand(), Ty, false),
 568                      createOrdering(&IRB, CASI->getSuccessOrdering()),
 569                      createOrdering(&IRB, CASI->getFailureOrdering())};
 570     CallInst *C = IRB.CreateCall(TsanAtomicCAS[Idx], Args);
 571     Value *Success = IRB.CreateICmpEQ(C, CASI->getCompareOperand());
 572
 573     Value *Res = IRB.CreateInsertValue(UndefValue::get(CASI->getType()), C, 0);
 574     Res = IRB.CreateInsertValue(Res, Success, 1);
 575
 576     I->replaceAllUsesWith(Res);
 577     I->eraseFromParent();
 578   } else if (FenceInst *FI = dyn_cast<FenceInst>(I)) {
 579     Value *Args[] = {createOrdering(&IRB, FI->getOrdering())};
 580     Function *F = FI->getSynchScope() == SingleThread ?
 581         TsanAtomicSignalFence : TsanAtomicThreadFence;
 582     CallInst *C = CallInst::Create(F, Args);
 583     ReplaceInstWithInst(I, C);
 584   }
 585   return true;
 586 }
 587
 588 int ThreadSanitizer::getMemoryAccessFuncIndex(Value *Addr,
 589                                               const DataLayout &DL) {
 590   Type *OrigPtrTy = Addr->getType();
 591   Type *OrigTy = cast<PointerType>(OrigPtrTy)->getElementType();
 592   assert(OrigTy->isSized());
 593   uint32_t TypeSize = DL.getTypeStoreSizeInBits(OrigTy);
 594   if (TypeSize != 8  && TypeSize != 16 &&
 595       TypeSize != 32 && TypeSize != 64 && TypeSize != 128) {
 596     NumAccessesWithBadSize++;
 597     // Ignore all unusual sizes.
 598     return -1;
 599   }
 600   size_t Idx = countTrailingZeros(TypeSize / 8);
 601   assert(Idx < kNumberOfAccessSizes);
 602   return Idx;
 603 }